The present invention relates to a thread insert. More specifically, the present invention relates to a helical thread insert having a removable tang for installation, a removal notch formed in the last thread of the insert and a retention device.
Helical thread inserts are used in many industries to provide female threads in a threaded bore located in a parent material having a relatively low hardness. The helical thread inserts are installed using a special tool that grasps a removable tang located at the leading end of the helical thread insert and guides the insert into the threaded bore in the parent material. The tang is then removed to provide a threaded bore having full thread engagement and female threads with a greater hardness than the female threads formed in the original threaded bore. In the event that the helical thread inserts become worn or damaged, removal of the thread insert may be required.
In recognition of the need to remove helical thread inserts several devices have been developed. Some helical thread inserts include a pair of diametrically opposed notches formed in the last thread of the insert. The notches allow a flathead screwdriver or other tool to apply a counterclockwise torque to guide the insert out of the original threaded bore. However, the use of a flathead screwdriver or other tool may apply forces that drive the insert back into the threaded bore or expand the last thread of the insert radially outward. If the tool applies a force on the insert that pushes the insert back into the original threaded bore, removal of the thread insert is made more difficult because the desired direction of movement of the insert, out of the hole, is opposite of the force that is applied on the insert. Additionally, if the tool causes expansion of the last thread of the insert, the end of the thread may dig into the parent material causing removal of the thread insert to be more difficult and possibly damaging the parent material. In recognition, thread inserts have been developed that have chamfered and radiused edges formed around the end of the last thread to prevent the thread from digging into the parent material.
However, one concern associated with helical thread inserts is retention capability, the ability of the insert to remain in the threaded bore. The use of chamfered or radiused ends reduces the ability of the end of the thread insert to grasp the parent material to prevent counterclockwise movement, leading to inadvertent removal of the insert. Additionally, the increasing popularity of stainless steel helical thread inserts in combination with stainless steel threaded fasteners may lead to galling. If galling occurs, the forces applied to the threaded fastener are directly transferred to the helical thread insert, thus increasing the likelihood that the helical thread insert will not remain in the threaded bore.
Accordingly, the present invention provides a helical thread insert having a tang for installation, a square end providing increased retention, and a removal notch. The tang is attached to a front end of the helical thread insert to provide a means of installing the insert. The square end prevents counterclockwise rotation of the insert, whereby counterclockwise rotation may lead to inadvertent removal of the insert. The removal notch provides a means of selectively removing the insert without engaging the retention device.
Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention.